Which is exactly why this only makes sense for large units (I would reckon far beyond 1k qty).
If you need to spend just 1 day debugging a lost-in-translation or undocumented feature, that easily adds up to 500 - 1k$ budget.
You could have bought 1500 PIC10s for that 1 day of debugging.
In addition, let's consider the hundred to thousand qty range. Can you get these chips preprogrammed? What tools do you need to do it yourself in a production environment? How much time does it take you to set this up and keep it running, and how fast is programming/verification?
Sure these problems are also very relevant for any other chip, but this is exactly part of the investment for a particular series of chip. See the aforementioned 1 day of debugging time cost.
Finally, these 3ct micro's are very small chips, so the code running on it will be very low level and direct approach.
But there are also cheap chips out there that can support USB, Ethernet, or any other protocol via software. How much in terms of SDK code is out there which you can pick up and just use? The SDK and code examples are a great place to start testing hardware and building their application on top of it, especially if you don't want to mess around for days or weeks writing, debugging, verifiying, reorganizing and refactoring code.